CN112004895B

CN112004895B - Alcohol-soluble printing ink composition

Info

Publication number: CN112004895B
Application number: CN201880092693.8A
Authority: CN
Inventors: 施剑秋
Original assignee: Eastman China Investment Management Co ltd
Current assignee: Eastman China Investment Management Co ltd
Priority date: 2018-04-24
Filing date: 2018-04-24
Publication date: 2022-10-21
Anticipated expiration: 2038-04-24
Also published as: WO2019204994A1; US20210047526A1; CN112004895A; EP3784741A1; EP3784741A4

Abstract

Disclosed herein are ink formulations that result in improved pigment dispersion and blocking resistance in alcohol-soluble inks. The ink composition comprises: at least one colorant; a bonding agent comprising polyurethane; a solvent system comprising at least about 50% by weight of an alcohol based on the total weight of the solvent system; and a cellulose ester selected from the group consisting of cellulose acetate propionate and cellulose acetate butyrate.

Description

Alcohol-soluble printing ink composition

Background

In recent years, increasing environmental and safety regulations have brought about the need for inks that are less toxic, less odorous, have less volatile organic compounds therein, are more cost effective and are suitable for various types of printing. Alcohol-soluble inks with alcohol-water solvent systems and/or alcohol/ester co-solvent systems have been considered for use as printable inks on flexible packaging, shrink labels, paper, cartons, and the like.

However, some alcohol-soluble inks still present technical hurdles. For example, for many alcohol-soluble inks, there is no suitable level of pigment dispersion or blocking resistance because commonly used linking agents, such as TPU (thermoplastic polyurethane) and/or TPA (thermoplastic polyacrylate), do not exhibit good dispersion and blocking resistance properties because they are optimized for other functions, such as adhesion or cohesion. These inks tend to have lower gloss, lower color strength, higher viscosity, more thixotropic rheology, more sedimentation, and more blocking. In addition, some conventional inks are formulated with acrylic resins, which are generally only suitable for white inks, not for colored inks.

Accordingly, there remains a need for ink compositions that use TPU and/or TPA linking agents, and which can provide excellent pigment dispersion and anti-blocking properties in alcohol-based solvent systems. In other ink systems, this improvement is achieved by the addition of a high molecular weight cellulose alkylate. However, such cellulose alkylate is incompatible with the alcohol/water solvent blends required in current ink systems.

Disclosure of Invention

An alcohol-soluble printing ink composition is described. The ink composition comprises: at least one colorant; a bonding agent comprising polyurethane; a solvent system comprising at least about 50% by weight of an alcohol based on the total weight of the solvent system; and a cellulose alkylate selected from Cellulose Acetate Propionate (CAP), cellulose Acetate Butyrate (CAB), cellulose Acetate Propionate Butyrate (CAPB), or mixtures thereof. The cellulose ester has (i) a hydroxyl content of 5.1% to 7.1% by weight, (ii) an acetyl content of 0.05% to about 0.65% by weight, both based on the weight of the cellulose ester, and (iii) a number average molecular weight (M) of 7,000 to 13,000g/mol _n )。

The solvent system comprises a solvent comprising a mixture of at least one alcohol and water. The alcohol may be ethanol, isopropanol, methoxypropanol, ethoxypropanol, or combinations thereof, and the solvent system comprises about 50% -90%, 50% -80%, 50% -70%, and/or 50% -60% by weight of the alcohol component. The system may also comprise a co-solvent of at least one alcohol and at least one ester. The ester may be selected from ethyl acetate, isopropyl acetate, n-propyl acetate, methoxypropyl acetate, or combinations thereof.

Drawings

FIG. 1 depicts the dilution curves of alcohol-soluble inks with different ratios between CAP and PU.

FIG. 2 depicts the bond strength of alcohol-soluble inks with different ratios between CAP and PU.

Detailed Description

An alcohol-soluble printing ink composition is provided. The ink composition is advantageously optimized to have superior adhesion, blocking resistance and dispersibility properties compared to prior art alcohol-soluble printing inks. The composition comprises at least one colorant, a bonding agent (desirably comprising a polyurethane), a solvent system, which in some embodiments comprises a solvent, a co-solvent, and/or both, wherein there is at least about 50% by weight alcohol based on the total weight of the solvent system. The composition further comprises a cellulose alkylate, which in embodiments may be Cellulose Acetate Propionate (CAP), cellulose Acetate Butyrate (CAB), cellulose Acetate Propionate Butyrate (CAPB), or a mixture thereof. Further, in some embodiments, the cellulose ester has a hydroxyl content of from about 5.1% to about 7.1%, and in other embodiments, from about 5.2% to about 7.0%, from about 5.3% to about 6.9%, from about 5.4% to about 6.8%, or from about 5.5% to about 6.5% by weight.

In some embodiments, the cellulose ester has an acetyl content of about 0.05% to about 0.65%, in other embodiments, about 0.05% to about 0.60%, about 0.05% to about 0.55%, about 0.05% to about 0.50%, or about 0.05% to about 0.45% by weight. Further, the number average molecular weight (M) of the cellulose ester _n ) From about 7,000 to about 13,000g/mol.

As the colorant, any type of colorant commonly used for inks may be used, including organic pigments, inorganic pigments, dyes, and the like. Although the alcohol-based printing ink composition of the present invention uses alcohol as a main component of a medium, the composition exhibits excellent pigment dispersibility not only for inorganic pigments but also for organic pigments.

Although not limited to the following examples, specific examples of the organic pigment include carmine 6B, lake red C, permanent red 2B, disazo yellow, pyrazolone orange, carmine FB, cromophor yellow (cromophtal yellow), cromophor red, phthalocyanine blue, phthalocyanine green, dioxazine violet, quinacridone magenta, quinacridone red, indanthrone blue, pyrimidine yellow, thioindigo purplish red (thioindo bordeaux), thioindigo magenta, perylene red, perinone orange (perinone orange), isoindolinone yellow, aniline black, diketopyrrolopyrrole red and daylight fluorescent pigments.

Examples of c.i. pigment numbers for organic pigments that can be used include, but are not limited to: c.i. pigment blue 15, c.i. pigment yellow 14, c.i. pigment yellow 17, c.i. pigment yellow 83, c.i. pigment yellow 155, c.i. pigment red 48.

Although not limited to the following examples, specific examples of the inorganic pigment include carbon black, aluminum powder, bronze powder, chrome vermilion, chrome yellow, cadmium red, ultramarine blue, prussian blue, red iron oxide, yellow iron oxide, iron black, titanium oxide, and zinc oxide.

Although not limited to the following examples, specific examples of the dye include tartrazine lake, rhodamine 6G lake, victoria pure blue lake, alkali blue G toner, and brilliant green lake. Coal tar and the like may also be used.

Among the various possibilities, it is desirable to use an organic pigment or an inorganic pigment in terms of water resistance and the like.

The colorant is contained in an amount such that: sufficient to ensure satisfactory colour density and colour strength of the printing ink. In other words, the content of the colorant (E) is, in some embodiments, in a proportion of from 1 to 50% by weight, and in other embodiments, from 5 to 40% by weight, relative to the total weight of the printing ink composition. These colorants may be used alone, or a combination of two or more colorants may be used.

As for the polyurethane, any type of polyurethane suitable for use as a bonding agent while not hindering the dispersion and anti-blocking properties may be used. One particularly useful polyurethane is the polyether polyurethane designated TA 2459A-1, which is commercially available from Hitachi Chemical company.

The alcohol-based printing ink composition of the present invention contains alcohol in a proportion of at least 50% by weight with respect to a value of 100% by weight of the entire medium, and when the proportion of alcohol is in the range of 50% by weight to 100% by weight, the composition exhibits good pigment dispersibility and re-solubility.

Although not limited to the following examples, specific examples of the alcohol include: aliphatic alcohols having 1 to 7 carbon atoms, such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol and tert-butanol, and glycol monoethers, such as propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monoisopropyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monoethyl ether, tripropylene glycol monopropyl ether and tripropylene glycol monobutyl ether.

Among the above alcohols, ethanol and/or isopropanol are preferably used from the viewpoint of reducing the environmental impact and ensuring a high volatilization rate. In addition, the proportion of ethanol and/or isopropanol is preferably at least 70% by weight relative to the value of 100% by weight of the total alcohol (F), with a proportion of ethanol of at least 70% by weight relative to the value of 100% by weight of the total alcohol (F) being particularly desirable. These alcohols (F) may be used alone, or a mixture containing two or more alcohols may be used.

The alcohol-based printing ink composition of the present invention may also contain water as a medium in order to enhance the dispersion stability of the pigment. The amount of water contained in the medium is preferably in the range of 2 to 20% by weight, more preferably 2 to 10% by weight, relative to a value of 100% by weight of the total medium. When the amount of water in the medium is not more than 20% by weight, the drying rate of the medium is fast and the production efficiency is high in the drying process of the printing ink. When the amount of water in the medium is at least 2% by weight, the pigment dispersion stability and storage stability are good.

The alcohol-based printing ink composition of the present invention may further include a solvent other than alcohol in the medium, if necessary. Although not limited to the following solvents, specific examples of such other solvents include methoxypropanol and ethyl acetate.

The method for producing the alcohol-based printing ink composition of the present invention is not particularly limited, and for example, the composition can be prepared by mixing a urethane resin, a medium, and a colorant, performing a pigment dispersion treatment using a dispersing device (e.g., a sand mill) to obtain a pigment dispersion as a precursor, and then diluting the precursor to obtain the alcohol-based printing ink composition. During this milling or grinding process, all the pigments, cellulose esters and part of the solvent or co-binder (co-binder) are blended into a mill base (millbase) with a solids content of 10% to 70% and bead-milled by means of a shaker (shaker), vertical mill or horizontal mill. High solids content and high viscosity will contribute to grinding efficiency. The millbase is then blended with the remaining portion of solvents, co-binders, and additives to produce the entire ink formulation.

The pigment dispersion treatment may be performed at a concentration that enables subsequent printing to be performed without further modification, but the dispersion treatment is preferably performed under the following conditions in terms of pigment dispersibility, color development characteristics, and production efficiency: wherein the concentration of the colorant is preferably 10 to 70% by weight, more preferably 20 to 50% by weight, within 100% by weight of the pigment dispersion. After the above pigment dispersion treatment is performed, the dispersion may be diluted with a resin and a medium or the like to obtain a concentration favorable for long-term storage.

In preparing the alcohol-based printing ink composition of the present invention, various types of additives may be used as necessary, including pigments, wetting agents, leveling agents, antifoaming agents, antistatic agents, blocking-resistant agents, and dispersing agents (e.g., vinyl chloride-vinyl acetate copolymers).

In particular, antiblocking agents, such as cellulose alkylates, e.g., cellulose Acetate Propionate (CAP) and Cellulose Acetate Butyrate (CAB), may be used in the alcohol-based printing ink compositions of the present invention.

In prior art ink compositions, it was necessary to use high molecular weight CAP or CAB to achieve the desired levels of blocking resistance and solubility parameters, but this was incompatible with the alcohol/water solvent systems required for current inks. Applicants of the present disclosure have discovered an optimal composition in which a low molecular weight CAP or CAB can be used in an ink formulation with a narrow range of acetyl and hydroxyl compositions to achieve the desired results with respect to compatibility, solubility, viscosity and rheological properties, and anti-blocking properties.

Examples of the invention

Cellulose ester formation

Cellulose (82 g) provided as cotton linters was activated with water, rinsed with acetic acid, and rinsed with propionic acid. At 2L of transThe kettle was charged with propionic acid-wet activated cellulose (162 g). Propionic acid (138 g) was added to the kettle. The mixture was cooled to 15 ℃. A mixture of propionic anhydride (319 g) and sulfuric acid (2.8 g) was cooled to 15 ℃ and then charged to the reaction kettle. The mixture was stirred at room temperature for 1h. The mixture was then heated to 63 ℃ over the course of 45 minutes and held for 45 minutes ("Hld/T"). A mixture of water (131 g) and propionic acid (371 g) was slowly added to the clear "dope". The mixture was stirred 1250min at 71 ℃ ("H/T"). By adding Mg (OAc) dissolved in AcOH (84 g) and water (64 g) ₂ (8g) To neutralize the catalyst. The neutralized dope was filtered through a coarse sintered funnel (coarse sintered funnel) covered with glass wool at room temperature. The clear neutralized concentrate was poured into 9L of water with rapid mixing to precipitate the product. The precipitate was washed thoroughly with deionized water overnight. The product was dried overnight in a vacuum oven at about 60 ℃ to give the final product. Molecular weight of CAP product (M) _n ) Is 12,670. Other CAP products described herein were produced using the same general procedure.

pigment/CE ratio

The ink formulations of the present disclosure contain about 0-15% organic pigment, 0-6% dispersion resin, and 6-20% primary binder. PU laminating inks (lamination inks) are formulated with CE, PU and pigment, where CE is the major contributor to pigment dispersibility. Herein, pigment Red 146, CE and PU are used to illustrate the performance difference by dose adjustment.

CE reference sample CAP2-5, 5.14% OH, molecular weight 7,610.PU references the commercially available polyether polyurethane product TA24-559A, available from Hitachi chemical company. The amounts of CE and PU were adjusted at a fixed total resin amount. Different ratios between CE and PU show different dilution curves and bond strengths.

Alcohol-soluble inks were formulated as shown in table 1 below. The ink formulation is divided into millbase and letdown (letdown) portions. The millbase is a high concentration pigment dispersion containing all pigments and CE. High viscosity, pigment and alkylated cellulose content increases dispersion efficiency. The dispersion was carried out by: mixing and bead milling with a laboratory vertical shaker, industrial mill or homogenizer as known in the art. The final millbase is then mixed with the letdown by stirring to give the final ink product. The letdown portion includes the remaining PU resin, solvent, and additives of the ink formulation.

The ink formulation of 1-1, which is applicable to all inks in Table 1 below, is now described. The millbase comprised 10.5 grams of pigment red 146, 19.8 grams of CAP2-5 solution (20% solids in ethanol/ethyl acetate = 4/1), 7.2 grams of TA24-559A (33% solids in ethanol/ethyl acetate = 1/2), and 10.3 grams of ethanol. 2.2 grams of ethyl acetate were filled into a 250ml fluorinated HDPE bottle and mixed with 100 grams of ceramic beads. Followed by vertical shaking with Fast & Fluid SK450 mixer for 2 hours. A letdown comprising 24.7 grams PU, 15.3 grams Ethanol (EA), 5.0 grams ethyl acetate (EAc), and 5 grams methoxypropanol (PM) was then added to the bottle and shaken for an additional 0.5 hours. The final ink product was filtered and checked by a grind gauge. The fineness is less than 15um.

TABLE 1 alcohol soluble ink formulations based on different CAP/PU ratios

The lower dilution curve shows the viscosity change as the dilution solvent is added to the ink. It is an important indicator of the printing process that will affect color intensity and print quality. Here, the viscosity was checked by Sheen 405/flow cup number 2 (flow cup) according to ASTM D4212 and D1084. Other flow cups that may be used are Toyo cups, nippo cups, ford cups, din cups, frikmar cups, TU cups, and the like. To check the ink viscosity, the flow cup was immersed in the ink, pulled out of the ink, and it was checked how much time it took for the continuous ink flow to break at the hole in the bottom of the flow cup. The ink was gradually diluted with a co-solvent of ethanol/ethyl acetate =4/1 until the flowcup viscosity reached 20 seconds. The dilution curves for inks 1-1 to 1-5 are shown in FIG. 1.

TABLE ink dilution ratio and cup viscosity vs. different CAP/PU ratios

* For Sheen 405/2 flow cups, the ink viscosity was too high for inks 1-2 to 1-5 at dilution ratio = 0.

After dilution, the ink is printed on biaxially oriented polypropylene (BOPP), biaxially Oriented Polyethylene (BOPET) and Biaxially Oriented Polyamide (BOPA) films using a RK proof press or an on-line printer. Then 1.5g/m2 solvent-borne (solvent-borne) 2K PU binder DIC LX-500 was coated onto the printed side by a # 2 doctor bar coater (K-bar coater) and PE and RCPP films were laminated onto the printed side by a conventional roll-to-roll press (roll-to-roll press) as known in the art. The 2K PU adhesive was cured at 40 ℃ for 24 hours. Typical laminate structures are BOPP/ink/binder/PE, BOPET/ink/binder/PE and BOPA/ink/binder/RCPP. After curing, the laminate film is cut into 15mm wide strips and the bond strength is checked by peeling the PE or RCPP from the BOPP, BOPET or BOPA using, for example, an INSTRON 5543 stretcher. BOPA laminates were re-inspected for bond strength after 30 minutes of heat steaming (retto) at 125 ℃. The bond strengths of ink 1-1 to ink 1-5 are shown in FIG. 2.

(BOPP = biaxially oriented polypropylene, BOPET = biaxially oriented polyester, BOPA = biaxially oriented polyamide, PE = polyethylene, RCPP = heat-evaporable cast polypropylene)

Bond strength vs. different CAP/PU ratios for different laminate structures

The dilution curve shows that the ink viscosity and dilution ratio become lower when more CAP-1 is used in place of the PU resin. This means that cellulose alkylate has better pigment dispersibility and ink printability than PU. The bond strength curve also shows that when more CAP-1 is used in place of PU, the lamination fastness becomes weaker. This means that the adhesion of the cellulose alkylate is less than that of PU. Therefore, the ink formulation needs to achieve a balance between pigment dispersibility and adhesion by optimizing the amounts of cellulose alkylate and PU, or by incorporating other adhesion promoting additives. Herein, we consider that the optimum range of cellulose alkylate/PU is around 0.20, and the bond strength value can satisfy the requirements of common laminated packaging (such as dry food, wet food and retort food bags).

After dilution, the inks were also printed on BOPP and BOPET to check the anti-blocking properties. Using 2kg/cm ² The pressure pressed the ink side onto the non-corona (scorona) side and stored at 50 ℃. After 24 hours, the overlapped films were peeled off by hand. The antiblock performance is rated from 0 to 5, according to the size of the blocked area, and is shown in the table.

TABLE antiblocking Properties vs. different CAP/PU ratios

Score adhesions at 5 to 0, 5= no adhesion zone, 0= total adhesion

The blocking resistance test showed that laminating inks with little or no cellulose alkylate (e.g., inks 1-5) showed severe blocking problems. The cellulose alkylate/PU ratio between inks 1-3 and inks 1-4 is necessary to have a sufficient antiblocking effect, which means that for the colored ink formulations the cellulose alkylate/PU is between 1/4.5 and 1/6.25.

Solubility in water

The new cellulose alkylate type is preferably high hydroxyl and low acetyl CAB or CAP, more preferably CAP for low odor packaging applications. CAP can be dissolved in alcohol/ester and alcohol/water co-solvents. For packaging ink applications, the alcohol may be ethanol, isopropanol, methoxypropanol, ethoxypropanol, and the like, and the ester may be ethyl acetate, isopropyl acetate, n-propyl acetate, methoxypropyl acetate, and the like.

Typical high hydroxyl and low acetyl CAP have similar solubility in alcohol/ester co-solvents, but very different solubility in alcohol/water co-solvents, which will be greatly affected by their hydroxyl content.

The chemical structures of CAPs with varying hydroxyl content from CAP2-1 to CAP2-7 are shown in Table 1. 20 grams of CAP was stirred into 80 grams of an alcohol/water co-solvent to form a solution of 20% solids content. 4 grams of CAP were stirred into 96 grams of an alcohol/water cosolvent to form a 4% solids solution. The solution was stored and observed for 30 days at room temperature. Sedimentation and gelling were visually observed, indicating insolubility. The ethanol/water and isopropanol/water solubilities of these CAP samples are shown in tables 2 and 3.

Chemical structures of CAP2-1 to CAP2-7

Sample number	ELN number	OH％	Pr％	Ac％	Mn
						CAP2-1	PP13-179	7.04％	37.6％	0.61％	10,851
CAP2-2	PP14-227	6.02％	41.5％	0.12％	12,667
						CAP2-3	PP14-226	5.76％	42.3％	0.00％	11,998
CAP2-4	PP15-220	5.63％	42.3％	0.46％	8,569
						CAP2-5	3158-020-3	5.14％	43.4％	0.59％	7,610
CAP2-6	Commercial CAP504-0.2	5.0％	42.5％	0.60％	15,000
						CAP2-7	Commercial CAP482-0.5	2.6％	45.0％	2.50％	25,000

Solubility of 20% solids CAP in alcohol/water solutions

Solubility of 4% solids CAP in alcohol/water solution

The solubility table shows: (1) different hydroxyl content has an effect on alcohol/water solubility, optimized hydroxyl ranges between CAP2-2 to CAP2-4, (2) isopropanol/water solubility is broader than ethanol/water, and (3) less solid solutions will require slightly more water in the co-solvent than more solid solutions.

Compatibility

The new CE type meets the compatibility required in practical ink applications. High hydroxyl and low acetyl CAB or CAP are formulated with polyurethanes, acrylics, rosin resins and plasticizers, among others. Therefore, compatibility between CAP and alcohol soluble polyurethane was examined by blending CAP solution/PU solution/ethanol in a ratio of 1/1/2. Herein, the CAP solution refers to a solution of 20% solids in ethanol/water =7/1 solvent, and the PU solution refers to a provided state with 33% solids. The mixture was stored and observed for 30 days at room temperature. Sedimentation and delamination were visually observed, indicating incompatibility.

The compatibility of CAP2-1 to CAP2-7 with selected PU samples was examined. The results are shown below.

PU candidates for compatibility testing

Trade name	Manufacturer of the product	General structure
			Neorez U-335	DSM	Fragrance composition
TA24-559A	Hitachi chemical Co Ltd	Non-aromatic
			Wancol 913	Wanhua (Wanhua)	Non-aromatic
Picassian PU-548	Stahl	Aromatic, low molecular weight

Compatibility of CAP with commercially available alcohol-soluble PU

	OH％	U-335	559A	913	548
						CAP2-1	7.04％	X	X	X	X
CAP2-2	6.02％	X	Y	Y	Y
						CAP2-3	5.76％	X	Y	Y	Y
CAP2-4	5.63％	X	Y	Y	Y
						CAP2-5	5.14％	X	Y	Y	Y
CAP2-6	5.0％	X	Y	Y	Y
						CAP2-7	2.6％	X	Y	Y	Y

Compatibility tests show that: (1) aromatic PUs are generally incompatible with CAP, (2) some non-aromatic PUs are compatible with CAP, depending on the polyol portion of the PU, such as TA24-559A and Wancol 913, and (3) some low molecular weight aromatic PUs, designed as plasticizers, are compatible with CAP. This type of compatible combination can be applied in surface printing ink formulations, (4) the hydroxyl content of CAP should be optimized to less than 7% for good compatibility.

Pigment dispersibility

CAP powder and NC wool were pre-dissolved in a 20% solids solution. 20 grams of CAP, 10 grams of ethyl acetate and 70 grams of isopropyl alcohol were mixed into the CAP solution by a stirrer or vertical shaker. 28.6 g of NC wool (30% isopropanol as wetting agent), 10 g of ethyl acetate and 61.4 g of isopropanol are mixed into the NC solution by means of a stirrer or vertical shaker.

The ink was treated in the same manner as the above ink. The ink formulation is divided into a millbase and a letdown portion. The millbase is first bead milled and then blended with the letdown. Color saturation and dilution ratio were introduced to evaluate the pigment dispersion of the ink formulations.

Color saturation represents color intensity and is positively correlated with pigment dispersion. The inks were printed on a standard Leneta P-300 carton using a K print proofer 81943-1 gravure or 2# doctor bar coater and then checked for color saturation using a colorimeter using the CIE's LCH method. Such colorimeters may be X-Rite eXact and Sheen Micromatch Plus.

Dilution ratio represents the rheological quality and is inversely related to pigment dispersibility. The ink was gradually diluted with solvent and checked with a viscosity cup.

Values for ink formulation, color saturation and dilution ratio are shown below.

CAP/PU and NC/PU based alcohol-soluble ink formulations

From the color saturation and dilution ratio, we can find that:

(1) In alcohol-based laminating inks, CAP has significantly higher color saturation and lower dilution ratio than NC, which helps to print more realistic images or reduce ink consumption.

(2) CAP2-2, with a higher hydroxyl content, has a higher color saturation than CAP2-5, which means that the dispersibility of the pigment can be improved by the higher hydroxyl content.

In the above tests, CAP was found to have better color intensity and dilution properties in alcohol-based inks compared to the traditional NC + PU system.

Claims

1. An alcohol-soluble printing ink composition comprising:

(a) At least one colorant;

(b) A bonding agent comprising polyurethane;

(c) A solvent system comprising at least 50% by weight of an alcohol, based on the total weight of the solvent system;

(d) A cellulose alkylate selected from the group consisting of cellulose acetate propionate and cellulose acetate butyrate,

wherein the cellulose alkylate has (i) a hydroxyl content of 5.1% to 7.1% by weight, and (ii) 0.05% to 0.45% by weight(ii) an acetyl content, both based on the weight of the cellulose ester, and (iii) a number average molecular weight (M) of from 7,000 to 13,000g/mol _n )。

2. The composition of claim 1, wherein the solvent system comprises a solvent comprising a mixture of at least one alcohol and water.

3. The composition of claim 2, wherein the at least one alcohol is ethanol.

4. The composition according to claim 2, wherein the at least one alcohol is isopropanol.

5. The composition of claim 2, wherein the at least one alcohol is selected from the group consisting of ethanol, isopropanol, methoxypropanol, ethoxypropanol, and combinations thereof.

6. The composition of claim 1, wherein the solvent system comprises 50% to 90% by weight of an alcohol.

7. The composition of claim 1, wherein the solvent system comprises 50% to 80% by weight of an alcohol.

8. The composition of claim 1, wherein the solvent system comprises 50% to 70% by weight of an alcohol.

9. The composition of claim 1, wherein the solvent system comprises 50% to 60% by weight of an alcohol.

10. The composition of claim 2, wherein the solvent system further comprises a co-solvent.

11. The composition of claim 10, wherein the co-solvent comprises a mixture of at least one alcohol and at least one ester.

12. The composition of claim 11, wherein the alcohol is ethanol.

13. The composition of claim 11, wherein the at least one alcohol is isopropanol.

14. The composition of claim 11, wherein the at least one alcohol is selected from the group consisting of ethanol, isopropanol, methoxypropanol, ethoxypropanol, and combinations thereof.

15. The composition of claim 11, wherein the at least one ester is ethyl acetate, isopropyl acetate, n-propyl acetate, methoxypropyl acetate, or a combination thereof.